03Fail-shake decay — on a failed match, the icon shakes left-right along a spring-damping value that settles to zero

<main class="stage">
<div class="fail-wrap">
<button type="button" class="fail is-demo" id="fail" aria-pressed="false">
  <svg class="fail__icon" id="icon" viewBox="0 0 120 120" aria-hidden="true">
    <circle class="fail__ring" cx="60" cy="60" r="34"></circle>
    <path class="fail__mark" id="mark" d="M46,46 L74,74 M74,46 L46,74"></path>
  </svg>
  <span class="fail__label">Fingerprint auth</span>
</button>
<p class="fail__status" id="status">Please try again</p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 계산 겹은 index.html 의 apply() 에 있다 — 감쇠 스프링 진동식(지수 감쇠 × 코사인)을 매 프레임
// 다시 계산해 아이콘 translateX 오프셋에 쓴다. 여기는 무대·모양만 맡는다.
@include stage($stage-ink);

.fail-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
}

.fail {
  appearance: none;
  border: none;
  background: transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
  cursor: pointer;
  padding: $sp-4;
  border-radius: $r-card;

  &:focus-visible { outline: 2px solid $error; outline-offset: 4px; }
}

.fail__icon {
  width: clamp(120px, 30vw, 160px);
  height: auto;
  overflow: visible;
}

.fail__ring {
  fill: none;
  stroke: $error;
  stroke-width: 3;
  opacity: .8;
}

.fail__mark {
  fill: none;
  stroke: $error-soft;
  stroke-width: 4;
  stroke-linecap: round;
}

.fail__label {
  color: $subject-cream;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.2;
  letter-spacing: .02em;
}

.fail__status {
  margin: 0;
  color: rgba($subject-cream, .58);
  font-weight: 500;
  font-size: 12px;
  line-height: 1.2;
}

@media (max-width: 340px) {
  .stage { padding: $sp-2; }
  .fail-wrap { gap: $sp-2; }
  .fail { padding: $sp-2 $sp-3; gap: $sp-2; }
  .fail__icon { width: 104px; }
  .fail__label { font-size: 12px; }
  .fail__status { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .fail__icon { transition: none; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.fail-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.fail {
  appearance: none;
  border: none;
  background: transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  cursor: pointer;
  padding: 16px;
  border-radius: 16px;
}
.fail:focus-visible {
  outline: 2px solid #c2361a;
  outline-offset: 4px;
}

.fail__icon {
  width: clamp(120px, 30vw, 160px);
  height: auto;
  overflow: visible;
}

.fail__ring {
  fill: none;
  stroke: #c2361a;
  stroke-width: 3;
  opacity: 0.8;
}

.fail__mark {
  fill: none;
  stroke: #ffe0d8;
  stroke-width: 4;
  stroke-linecap: round;
}

.fail__label {
  color: #fff7e6;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.2;
  letter-spacing: 0.02em;
}

.fail__status {
  margin: 0;
  color: rgba(255, 247, 230, 0.58);
  font-weight: 500;
  font-size: 12px;
  line-height: 1.2;
}

@media (max-width: 340px) {
  .stage {
    padding: 8px;
  }
  .fail-wrap {
    gap: 8px;
  }
  .fail {
    padding: 8px 12px;
    gap: 8px;
  }
  .fail__icon {
    width: 104px;
  }
  .fail__label {
    font-size: 12px;
  }
  .fail__status {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .fail__icon {
    transition: none;
  }
}

(function () {
  // 계산 겹: 감쇠 스프링 진동 — x(t) = AMPLITUDE * e^(-t/decayMs) * cos(t*FREQ). 트윈 이징이 아니라
  // 매 프레임 이 식으로 오프셋을 계산해 아이콘을 흔든다. SHAKE_DAMP 가 클수록 decayMs 가 커져
  // 진동이 오래 남고, 작을수록 빨리 잦아든다.
  var AMPLITUDE = 14; // 최대 흔들림 폭(px)
  var FREQ = 0.028; // 각속도(rad/ms)
  var SHAKE_DAMP = 18; // 변형 03: SHAKE_DAMP 18 → 8 (댐핑 — 작을수록 빨리 잦아든다)
  var SETTLE_MS = 900; // 이 시간이 지나면 진동을 멈추고 0 으로 고정한다
  var GAP_MS = 900; // 다음 자동 실패 시연까지 대기 시간
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var decayMs = reduce ? 1 : SHAKE_DAMP * 40;

  var root = document.getElementById('fail');
  var icon = document.getElementById('icon');
  var status = document.getElementById('status');
  var STRINGS = { idle: 'Please try again', failed: 'Auth failed' };
  var isDemo = true;
  var running = false;
  var startTs = 0;

  function apply(t) {
    var offset = AMPLITUDE * Math.exp(-t / decayMs) * Math.cos(t * FREQ);
    icon.style.transform = 'translateX(' + offset.toFixed(2) + 'px)';
  }

  function runShake(ts) {
    if (!startTs) startTs = ts;
    var t = ts - startTs;
    if (t <= SETTLE_MS) {
      apply(t);
      requestAnimationFrame(runShake);
    } else {
      apply(0);
      status.textContent = STRINGS.idle;
      running = false;
      root.setAttribute('aria-pressed', 'false');
    }
  }

  function trigger() {
    if (running) return;
    running = true;
    startTs = 0;
    status.textContent = STRINGS.failed;
    root.setAttribute('aria-pressed', 'true');
    requestAnimationFrame(runShake);
  }

  function human() { if (isDemo) { root.classList.remove('is-demo'); isDemo = false; } }

  root.addEventListener('click', function () { human(); trigger(); });
  root.addEventListener('keydown', function (e) {
    if (e.key === ' ' || e.key === 'Enter') { human(); }
  });

  apply(0);

  var cycleStart = 0;
  var PERIOD = SETTLE_MS + GAP_MS;
  function loop(ts) {
    if (isDemo && !reduce) {
      if (!cycleStart) cycleStart = ts;
      var phase = (ts - cycleStart) % PERIOD;
      if (phase < 16 && !running) trigger();
    }
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

// FailShake — vanilla 판(run/371/demo/03-biometric-scan-fail-shake/index.html) 의 React 포트.
// 계산 겹(감쇠 스프링 진동)은 useFailShake 훅 안에 있다: x(t) = AMPLITUDE * e^(-t/decayMs) * cos(t*FREQ)
// 을 매 프레임 다시 계산해 아이콘 translateX 오프셋에 쓴다.
import { useEffect, useRef, useState } from "react";
import styles from "./FailShake.module.scss";

type Box<T> = { current: T };

const STRINGS: Record<string, string> = { idle: "다시 시도해 주세요", failed: "인증 실패" };

function useFailShake(
  rootRef: Box<HTMLButtonElement>,
  iconRef: Box<SVGSVGElement>,
  setStatus: (s: string) => void,
  setPressed: (b: boolean) => void
) {
  useEffect(() => {
    const AMPLITUDE = 14;
    const FREQ = 0.028;
    const SHAKE_DAMP = 18; // 변형 03: SHAKE_DAMP 18 → 8
    const SETTLE_MS = 900;
    const GAP_MS = 900;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    const decayMs = reduce ? 1 : SHAKE_DAMP * 40;

    const root = rootRef.current;
    const icon = iconRef.current;
    if (!root || !icon) return;

    let isDemo = true;
    let running = false;
    let startTs = 0;
    let rafId = 0;

    function apply(t: number) {
      const offset = AMPLITUDE * Math.exp(-t / decayMs) * Math.cos(t * FREQ);
      icon.style.transform = "translateX(" + offset.toFixed(2) + "px)";
    }

    function runShake(ts: number) {
      if (!startTs) startTs = ts;
      const t = ts - startTs;
      if (t <= SETTLE_MS) {
        apply(t);
        rafId = requestAnimationFrame(runShake);
      } else {
        apply(0);
        setStatus(STRINGS.idle);
        running = false;
        setPressed(false);
      }
    }

    function trigger() {
      if (running) return;
      running = true;
      startTs = 0;
      setStatus(STRINGS.failed);
      setPressed(true);
      rafId = requestAnimationFrame(runShake);
    }

    function human() { if (isDemo) { root.classList.remove(styles.isDemo); isDemo = false; } }
    function onClick() { human(); trigger(); }
    function onKeyDown(e: KeyboardEvent) { if (e.key === " " || e.key === "Enter") human(); }
    root.addEventListener("click", onClick);
    root.addEventListener("keydown", onKeyDown);

    apply(0);

    let cycleStart = 0;
    const PERIOD = SETTLE_MS + GAP_MS;
    function loop(ts: number) {
      if (isDemo && !reduce) {
        if (!cycleStart) cycleStart = ts;
        const phase = (ts - cycleStart) % PERIOD;
        if (phase < 16 && !running) trigger();
      }
      rafId = requestAnimationFrame(loop);
    }
    rafId = requestAnimationFrame(loop);

    return () => {
      root.removeEventListener("click", onClick);
      root.removeEventListener("keydown", onKeyDown);
      cancelAnimationFrame(rafId);
    };
  }, []);
}

export default function FailShake() {
  const rootRef = useRef(null) as unknown as Box<HTMLButtonElement>;
  const iconRef = useRef(null) as unknown as Box<SVGSVGElement>;
  const [status, setStatus] = useState(STRINGS.idle);
  const [pressed, setPressed] = useState(false);

  useFailShake(rootRef, iconRef, setStatus, setPressed);

  return (
    <main className={styles.stage}>
      <div className={styles.failWrap}>
        <button
          type="button"
          className={styles.fail + " " + styles.isDemo}
          ref={rootRef}
          aria-pressed={pressed}
        >
          <svg className={styles.failIcon} viewBox="0 0 120 120" aria-hidden="true" ref={iconRef}>
            <circle className={styles.failRing} cx={60} cy={60} r={34} />
            <path className={styles.failMark} d="M46,46 L74,74 M74,46 L46,74" />
          </svg>
          <span className={styles.failLabel}>지문 인증</span>
        </button>
        <p className={styles.failStatus}>{status}</p>
      </div>
    </main>
  );
}